Solvothermal synthesis of crystalline nickel oxide nanoparticles

Nickel oxide (NiO) nanoparticles were synthesized via a solvothermal reaction with nickel(II) acetylacetonate as the metal containing precursor and 2-butanone (methyl ethyl ketone, MEK) as the solvent. The particles were characterized using X-ray diffraction, electron microscopy, Brunauer–Emmett–Teller (BET) surface area measurements and thermal gravimetric analysis (TGA) to determine that the crystal structure, particle size, and the presence of residual organic material upon completion of the reaction. The effect of varying the reaction temperature, time and metal precursor concentration were investigated. A range of optimal reaction conditions; defined here as a high yield, low residual organic content; were determined. A particle size in the range of 5.5–6.5 nm was observed for the optimal reaction conditions. The formation of metallic Ni was also observed for reactions carried out at 225 °C and time durations longer than 24 h. The reaction mechanism for the formation of NiO nanoparticles was investigated using mass spectrometry and a proposed pathway based on a keto-enol tautamerization is presented.